In a satisfying return to Norton's Time Trader world, a young man finds himself as he teaches guerrilla warfare to a feudal, nonterrestrial offshoot of humanity in order to prepare them properly for a future in which space- and time-traveling humans are battling for survival against murderous aliens. Ross Murdock, a young criminal recruited as a Time Agent for his survival skills, is sent to the Dominion of Virgin, which had abruptly turned from a populous planet to a burned cinder as a result of time-travel by the Baldies, as the aliens are known. The key development that would have saved the planet was the evolution of mental powers that were delayed because of the turmoil following a warlord's conquests 700 years previously. Murdoch, scientist Gordon Ashe and arms expert Eveleen Riordan are sent back in time to Dominion to develop a resistance movement without revealing the existence of Earth or drawing the attention of the Baldies. The authors, who collaborated on Redline the Stars and several Witch World books, have developed an attractive world and likable characters. This coming-of-age novel may be better suited for the young-adult market, however. (July)